A Method of the Inverse Evaluation for Heat Transfer Coefficient between Al-Cu Alloys and Cooling Water

Abstract:

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The heat transfer coefficient between the alloys and cooling water is affected by a lot of factors and hard to measure, a new method was investigated with a self-designed system ultilizing SP-15 high-frequency inductive heating unit. Based on measured temperature curves and Fourier heat transfer model, quantitative correlation between heat transfer coefficient and temperature was obtained by inverse algorithm method of iterative simulation and automatic optimization. The results showed that in submerged water-cooling process, the heat transfer coefficient reached to a peak value at the beginning and then decreased with increasing temperature. A decrease of cooling water temperature increased the peak value of the heat transfer coefficient, but did not change temperature range of the peak value from 200°C to 225°C . The heat transfer coefficient was mainly dependent of interfacial temperature between the Al-Cu alloys and the cooling water.The temperatures range from 200°C to 225°C gave the highest heat flux transfer.

Abstract: A two-dimensional orthogonal thermal-mechanical finite element model by Deform2D finite element analysis software is established in the article. By the adaptive meshing technique, not only cutting process but also the effect on the process of aluminum alloy Al6061-T6 processing as friction coefficient changing is simulated. The simulation shows that the friction coefficient has significant effect on the cutting temperature and cutting force, and the effect is nonlinear. With the increasing of the friction coefficient, the cutting temperature and cutting force will both increase. The impact the friction coefficient has on the surface residual stress is much smaller than the impact on the cutting temperature and cutting force.

Abstract: A distributed parameter method has been established for a ground-source heat pump in this paper, with this model, the working process of this heat pump system was simulated. The results agree well with experimental data and show that heat-capacity and COP increase when the cooling water flow rate in the tube-in-tube heat exchanger increases; heat-capacity decreases when the temperature of inlet water of the tube-in-tube heat exchanger rises; COP, between 3.8 and 4.5, is higher than that of conventional air-source heat pumps.

Abstract: Numerical method was used to simulate the solidification process of zinc-aluminum alloy Zamak 5, shrinkage porosity of the zinc-aluminum alloy ingot with big diameter (114mm) was simulated using the shrinkage criterion, orthogonal test was designed to analysis the influence of different casting parameters as casting temperature, preheating temperature of the mold and the heat transfer coefficient between the mold and the environment. The result shows that the shrinkage value was minimal when the casting temperature was 480, the preheating temperature was 200 and the heat transfer coefficient was 200.

Abstract: According to two parameters combination of the material thickness and air-gap depth, from the angle of pure optimization, this paper obtained the optimal parameters of single cavity and double cavity structure by using the simulated annealing algorithm for single cavity and double cavity of aluminum foam sound absorption structure of systematically optimization design at 100-4000HZ frequency band. Finally, studying effect of increasing the number of cavity on aluminum foam sound absorption properties.

Abstract: A new method for determination of friction coefficient in sheet metal forming of Mg alloy AZ31B is presented in this paper. The method is based on the bulging test of sheet metal in which the specimen is processed with a hole at the center. The diameter of the hole will increase along the stroke of the punch and the dimensional change of the hole has a certain relationship with the friction coefficient at the punch/specimen interface. Thus, the friction coefficient can be determined indirectly according to the dimension of the hole in the bulging process. The bulging process of the sheet is simulated using FE code DEFORM-2D. The analysis model is set up according to the experiment of the bulging and the friction calibration curves are generated from the simulations of the bulging by setting different coefficients of friction. The friction coefficient can be determined by measuring the hole dimension during the bulging process and comparing it with the friction calibration curves.